Some automatic transmissions include an input member, an output member, a stationary member, and intermeshing gears such as planetary gearsets, or gears arranged on layshafts or countershafts. One or more selectively engageable torque transmitting devices, i.e., clutches and brakes, selectively couple various gears to other gears or to the stationary member to achieve a plurality of different speed ratios between the input member and the output member. An all-wheel drive unit of a vehicle powertrain also typically includes a selectively engageable torque-transmitting device.
In a typical automatic transmission or other portion of a powertrain, such as an all-wheel drive unit on a vehicle powertrain, the torque transmitting devices are hydraulically actuated. A hydraulic circuit that includes a pump and solenoid valves are needed to control the application of fluid pressure to each of the torque transmitting devices.